shared_experts+router_experts merge all_reduce(Improve TTOP 5ms) (#1395)

### What this PR does / why we need it?
When all_reduce_merge is in progress, shared_experts does not do
all_reduce in mlp, but waits until shared_experts+router_experts are
completed before doing all_reduce
In prefill and decode, as long as shared_experts+router_experts are
all_reduce, there will be benefits.
### Does this PR introduce _any_ user-facing change?

### How was this patch tested?
bash examples/run_dp_attention_etp16.sh
bash examples/run_dp_attention_etp16_benmark.sh
- vLLM version: v0.9.1
- vLLM main:
977180c912

---------

Signed-off-by: ttanzhiqiang <389825161@qq.com>

vllm_ascend/utils.py

@@ -425,6 +425,20 @@ class FusedMoEState(Enum):
     NaiveMulticast = 4
 
 
+# TODO(ttanzhiqiang): all_reduce merge
+# When all_reduce_merge is in progress, shared_experts does not do all_reduce in mlp, but waits until shared_experts+router_experts are completed before doing all_reduce
+# Currently, all_reduce_merge is enabled by default in the AllGather, AllGatherEP and NaiveMulticast scenarios of the deepseek model.
+def get_all_reduce_merge_state(ep_size: int, is_deepseek_v3_r1: bool):
+    # the fusion operator torch_npu.npu_grouped_matmul_finalize_routing called by allgather ep
+    # only supports deepseek v3/r1
+    if (envs.VLLM_ENABLE_FUSED_EXPERTS_ALLGATHER_EP and ep_size > 1
+            and is_deepseek_v3_r1):
+        return True
+    elif ep_size == 1 and is_deepseek_v3_r1:
+        return True
+    return False
+
+
 # TODO(zzzzwwjj): add soc_version to choose branch
 def get_fused_moe_state(ep_size: int, with_prefill: bool,
                         is_deepseek_v3_r1: bool):